(1) Field of the Invention
The present invention relates to a resin composition for sealing liquid crystal cells, more specifically to a novel UV-curing type resin composition for sealing liquid crystal cells, which can be used under diversification of displays in recent years and severe environment and which is suited for sealing liquid crystal displays to which high reliability is required.
(2) Description of the Related Art
In recent years, improvements in electronics has rapidly been advanced mainly in personal computers, sound equipment, measuring instruments and color televisions. As a result, display systems using liquid crystals have widely been adopted. This is considered as being due to characteristics such as very small power consumption, low driving power, sufficient sharpness even under sun light and sharp contrast between light and shade, and due to the facts that miniaturization and light weight have been effectuated and low prices have been achievable and that a coloring technique using liquid crystals has reached such level as excels a Braun tube (CRT). Because of such advantages, the application fields of liquid crystal displays (LCD) have been going to a phase of increasing expansion.
This phase has been followed by active investigations on an elevation in the quality of LCD and an enhancement in productivity. Above all, a reduction in curing temperatures in a production process of a liquid crystal cell and maintenance of high reliability as well as shortening of a curing time have strongly been desired. This contributes largely to energy saving in producing liquid crystal cells and a reduction in production costs and prices of the products.
Epoxy resins are usually used for resins for sealing liquid crystal. In former times, two liquid hot-setting type epoxy resins were used, and used at present are single liquid hot-setting type epoxy resins (for example, Japanese Patent Laid-Open No. Sho 57-137317, Japanese Patent Laid-Open No. Sho 59-157330, Japanese Patent Laid-Open No. Hei 6-75231 and Japanese Patent Laid-Open No. Hei 6-73164). On the other hand, in recent years, UV-setting type acrylic adhesives and epoxy adhesives have been investigated, and, for example, UV-setting type acrylic adhesives are disclosed in Japanese Patent Laid-Open No. Sho 59-137929, Patent Laid-Open No. Hei 1-243029 and Patent Laid-Open No. Hei 3-188186, and UV-setting type epoxy adhesives are disclosed in Japanese Patent Laid-Open No. Sho 61-34477 and Patent Laid-Open No. Hei 1-254786.
However, the fact is that any of these adhesives can not sufficiently satisfy requirements such as a reduction in a curing temperature, shortening of a curing time and high reliability. That is, in the case of two liquid epoxy resins, since the pot life is short and the viscosity is liable to increase, the workability, yield and productivity are inferior. Even in the case of currently prevailing single liquid hot-setting type epoxy resins, a curing time of 60 minutes or longer at a temperature of 150.degree. C. is usually needed, and when they are cured at a further lower temperature of 130.degree. C., it takes a long time of 2 hours or more until needed performances are revealed. Accordingly, they are not suited for shortening of a curing time.
In the case of existing UV-curing type acrylic adhesives, a reduction in the curing temperature and shortening of the curing time are possible, but the workability and the pattern maintenance are inferior. Further, as revealed in a reliability test is the problem that the moisture resistance and the adhesive property are not sufficient. UV-curing type epoxy adhesives have hardly been put into practical use because of the problem of electrode corrosion as well as almost the same reasons as described above.